White space (hereafter referred to as “WS”) refers to a frequency domain in a specific frequency band allocated to a service using radio wave such as broadcast and communication but not being in use. As the demand for wireless communication increases in recent years, effective use of the WS has been considered. The usage of the WS includes broadband services for general public, local one-segment broadcasting, disaster prevention broadcasting, emergency broadcasting, tour guides, and so on, and the WS must be shared by these various usages.
Accordingly, it is necessary for a WS user (secondary user) to first find out an available channel (frequency) by referring to frequency database information owned by a frequency database apparatus so as to avoid interference on the primary system (primary user).
As a method for sharing a WS by WS users, the WS is used after confirming, by sensing or others, that the WS users nearby are not interfered. Alternatively, in order to avoid the interference more securely, the WS user himself registers that a WS is used on the frequency database, so that other WS users are excluded as another method. In the following description, the latter will be described with reference to FIG. 1 and FIG. 2.
FIG. 1 is a sequence diagram for describing a WS sharing control method. In FIG. 1, in step (hereafter abbreviated as “ST”) 11, a frequency database apparatus regularly obtains information regarding a channel (channel #1: Ch. #1) used by the primary system (primary system information). In ST12, the frequency database apparatus updates frequency database information related to an available channel and an unavailable channel for the WS user.
In ST13, the second WS wireless device for application B (hereafter simply referred to as “second WS wireless device”) refers to the frequency database information held by the frequency database apparatus. In ST14, the second WS wireless device obtains information on an available channel. In addition, in ST15, the second WS wireless device registers a channel to be used on the frequency database held by the frequency database apparatus. In this method, the available channels are channels #2 to 4 (Ch. #2 to 4), and the channels used by the second WS wireless device are also channels #2 to 4.
In ST16, the frequency database apparatus updates frequency database information based on the registration by the second WS wireless device.
In ST17, the first WS wireless device for application A (hereafter simply referred to as “first WS wireless device”) refers to the frequency database information owned by the frequency database apparatus as a WS channel use request. In ST18, the first WS wireless device obtains the determination result that the channel is not available. As described above, it is possible to avoid the interference between WS users of different applications, that is, between the first WS wireless device for application A and the second WS wireless device for application B.
FIGS. 2A and 2B represent update statuses of frequency database information in the WS sharing control method illustrated in FIG. 1. FIG. 2A represents frequency database information before the update at ST16 in FIG. 1. More specifically, the frequency database information represents that the channel #1 (Ch. #1) is used by the primary system, and the channels #2 to 4 (Ch. #2 to 4) are available for WS for application A and for application B.
FIG. 2B represents frequency database information after the update at ST16 in FIG. 1. More specifically, the frequency database information represents that channel #1 (Ch. #1) is used by the primary system, and channels #2 to 4 (Ch. #2 to 4) are used by the second WS wireless device for application B. As a result, it is determined that the channels #1 to 4 (Ch. #1 to 4) are unavailable for application A.